"I don't even carry it on my trucks, I just know it's a highly restrictive product," Gallindo said. "It requires a certain certification and credentials to even get that."

Aluminum phosphide is used to kill insects and burrowing rodents. According to the EPA, there are 23 registered products in the U.S.

AFD said the children's father purchased the aluminum phosphide and used it under the home, but residents inside began getting sick. The father then tried to wash the pesticide away and dilute it, but that caused a reaction producing the phosphine gas.

The poison is not to be used within 15 feet of a home or building. In 2010, two children died in Utah after a pest treatment on their home.